JP5421952B2 - Ignition system - Google Patents

Description

  The present invention relates to an ignition system used for an internal combustion engine or the like.

  An ignition system used in a combustion apparatus such as an internal combustion engine includes a spark plug having a center electrode and a ground electrode, with a gap formed between both electrodes, and a discharge of an ignition coil or the like that supplies a voltage to the spark plug. There is known a power source for power supply and an ignition cable for electrically connecting a spark plug and a power source for discharge. In such an ignition device, a spark discharge is generated in the gap of the spark plug by applying a high voltage from the discharge power source to the spark plug via the ignition cable, and as a result, the fuel gas is ignited. It is like that.

  In recent years, in order to further improve the ignitability, a technique has been proposed in which spark discharge is generated by supplying AC power (high-frequency power) from an AC power source to the gap instead of high voltage. (For example, refer patent document 1 etc.).

JP 2009-8100 A

  However, in the above technique, since the spark is generated only by the AC power, the required voltage may not be output depending on the state in the combustion chamber. Therefore, a situation in which spark discharge does not occur (so-called misfire) is likely to occur even when power is turned on.

  On the other hand, to prevent the occurrence of misfire, it is conceivable to increase the AC power and output the required voltage more reliably. For example, in order to increase the output, the AC power is increased by a factor of two. The situation can only be improved inefficiently. On the contrary, there is a possibility that the center electrode and the ground electrode are more easily worn out due to the increase in electric power.

  This invention is made | formed in view of the said situation, The objective is to provide the ignition system which can implement | achieve the outstanding ignitability, suppressing generation | occurrence | production of misfire.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. The ignition system of this configuration includes a spark plug,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
The cylindrical AC electrode is disposed on the inner periphery of the second insulator,
The cylindrical insulator is disposed on the inner periphery of the AC electrode,
The discharge electrode is disposed on the inner periphery of the insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug .

  According to the above configuration 1, the spark plug is caused to generate a spark by the voltage supplied from the discharge power source, and then the AC power from the AC power source is input to the spark. Accordingly, the spark is strengthened by the AC power, and the spark can be grown larger, and as a result, the ignitability can be dramatically improved.

  In addition, since a spark is generated by applying a voltage, it is difficult to cause a situation in which the required voltage cannot be output as in the case of generating a spark by supplying only AC power, and the occurrence of misfire can be more reliably prevented. it can.

By the way, when supplying both spark discharge voltage and AC power to the spark plug, current flows from the discharge power source to the AC power source, and sufficient voltage is applied to the spark plug. There is concern about not being done. In this regard, according to the configuration 1, the ignition cable that electrically connects the ignition plug, the discharge power source, and the AC power source includes the discharge electrode, the AC electrode, and the insulator sandwiched between the electrodes. In addition, a capacitor formed by both the electrodes and the insulator is interposed between the spark plug and the AC power source. Therefore, AC power with a relatively high oscillation frequency is transmitted through the capacitor and inserted into the spark plug, while a relatively low frequency current output from the discharge power source is present in the capacitor. This suppresses the inflow to the AC power supply side. Therefore, a sufficient voltage can be applied to the spark plug, and a spark can be generated more reliably. As a result, the above-described effect of improving the ignitability can be more reliably exhibited.
In addition, according to the configuration 1, the dielectric constant of the insulator constituting a part of the capacitor is larger than the dielectric constant of the second insulator arranged on the outer periphery of the capacitor. Therefore, it is possible to more reliably prevent the AC power input to the capacitor (AC electrode) from being transmitted to the low potential side of, for example, an engine equipped with a spark plug through the second insulator. can do. As a result, the loss of AC power during transmission can be more reliably reduced, and sparks can be grown more effectively.

  Although inflow of current from the AC power supply side to the discharge power supply side can be considered, a discharge power supply for generating a spark generally includes, for example, a coil such as an ignition coil. Therefore, the current flowing from the AC power supply side to the discharge power supply side is prevented by the presence of the coil having the property of blocking the high frequency and transmitting the low frequency.

Configuration 2. The ignition system of this configuration includes a spark plug,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator is greater than the dielectric constant of the second insulator;
The discharge electrode, at least a part of which is cylindrical, is disposed on the inner periphery of the second insulator,
The cylindrical insulator is disposed on the inner periphery of the cylindrical portion of the discharge electrode,
The AC electrode is disposed on the inner periphery of the insulator,
The spark plug side end of the discharge electrode is configured to be connected to the spark plug.

According to the said structure 2, the effect similar to the said structure 1 is show | played fundamentally.

Configuration 3. The ignition system of this configuration includes a spark plug,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator is greater than the dielectric constant of the second insulator;
At least a part of the discharge electrode has a plate shape,
Of the AC electrode, at least a portion facing the plate-like portion of the discharge electrode has a plate shape,
The insulator is disposed between the plate-like portion of the discharge electrode and the plate-like portion of the AC electrode,
The electrodes and the insulator are disposed on the inner periphery of the second insulator,
The spark plug side end of the discharge electrode is configured to be connected to the spark plug.

According to the said structure 3, the effect similar to the said structure 1 etc. is show | played fundamentally.

Configuration 4. The ignition system of this configuration includes a spark plug,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator is greater than the dielectric constant of the second insulator;
In a cross section perpendicular to the longitudinal direction, at least a part of the discharge electrode has a spiral shape,
Of the alternating current electrode, at least a portion facing the spiral portion of the discharge electrode has a spiral shape,
The insulator is disposed between the spiral portion of the discharge electrode and the spiral portion of the AC electrode,
The discharge electrode, the AC electrode, and the insulator are disposed on an inner periphery of the second insulator,
The spark plug side end of the discharge electrode is configured to be connected to the spark plug.

According to the said structure 4, the effect similar to the said structure 1 etc. is show | played fundamentally.

Configuration 5. The ignition system of this configuration includes a spark plug,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator is greater than the dielectric constant of the second insulator;
The ignition cable is
The discharge electrode includes a first main electrode plate extending along a longitudinal direction, and a plurality of first auxiliary electrode plates extending from the first main electrode plate and arranged along a direction orthogonal to the longitudinal direction,
The AC electrode includes a second main electrode plate extending along the longitudinal direction, and a plurality of second auxiliary electrode plates extending from the second main electrode plate and arranged along a direction orthogonal to the longitudinal direction,
The discharge electrode and the AC electrode are arranged so that the first main electrode plate and the second main electrode plate face each other and the first auxiliary electrode plate and the second auxiliary electrode plate are alternately arranged. And
The insulator is disposed between the auxiliary electrode plates;
The discharge electrode, the AC electrode, and the insulator are disposed on an inner periphery of the second insulator,
The spark plug side end of the discharge electrode is configured to be connected to the spark plug.

According to the said structure 5, the effect similar to the said structure 1 etc. is show | played fundamentally.

Configuration 6 . In the ignition system of this configuration, in any of the above configurations 1 to 5, the oscillation frequency of the AC power is 50 kHz or more and 100 MHz or less,
The capacitance of the capacitor formed by the discharge electrode, the alternating current electrode, and the insulator is C (F),
When the oscillation frequency of the AC power is f (Hz),
C ≧ 0.0005 (F · Hz) / f
It is characterized by satisfying.

According to the configuration 6 , the AC power oscillation frequency is set to a sufficiently small value of 100 MHz or less. Therefore, for example, when the oscillation frequency of the AC power is extremely increased, the wavelength of the AC power becomes extremely short. As a result, resonance occurs inside the spark plug or the ignition cable, which may hinder the input of the AC power. Although it is feared that it will occur, according to the above configuration 2, the wavelength of the AC power can be made sufficiently large, and the above-mentioned concerns can be eliminated. That is, according to the configuration 2, the occurrence of resonance in the spark plug or the ignition cable can be more reliably prevented, and the above-described effect of improving the ignitability can be more reliably exhibited. In addition, since it is possible to prevent the occurrence of resonance without finely adjusting the design of the spark plug, etc., it is possible to secure a sufficient degree of freedom in the design of the spark plug and the like, and in addition, special adjustments have been made to the spark plugs that have been used in the past. It can be used as it is without applying.

In addition, according to the configuration 6 , the capacitance C (F) of the capacitor satisfies C ≧ 0.0005 (F · Hz) / f with respect to the oscillation frequency f (Hz) of the AC power. Is set. Therefore, when the AC power passes through the capacitor, the loss of AC power is further reduced, and as a result, the ignitability can be further improved.

Configuration 7 . The ignition system of this configuration is characterized in that, in any of the above configurations 1 to 6, the insulator is formed of a composite material of ceramic and resin or rubber.

According to the configuration 7 , the insulator is formed of the composite material made of ceramic and resin or rubber. Therefore, the resin or rubber functions as a buffer material against a mechanical shock or a thermal shock, and the peeling of the ceramic from the discharge electrode or the AC electrode accompanying the shock can be more reliably prevented. As a result, the durability of the capacitor can be further increased, and excellent ignitability can be maintained for a longer period of time.

  Furthermore, by providing resin or rubber, the flexibility of the ignition cable can be increased, and the handling of the ignition cable can be made easier.

Configuration 8 . The ignition system of this configuration is characterized in that, in any of the above configurations 1 to 6, the insulator is made of ceramic.

According to the configuration 8 , since the insulator is made of ceramic having excellent heat resistance and voltage resistance, the durability of the capacitor can be improved. As a result, excellent ignitability can be maintained over a longer period.

Configuration 9 . The ignition system of this configuration is characterized in that, in the above configuration 7 or 8 , the ceramic is mainly composed of barium titanate (BaTiO ₃ ).

According to the above configuration 9 , BaTiO _{3 that} is particularly excellent in terms of heat resistance among ceramics is used for the ceramic that constitutes the insulator. Therefore, the durability of the capacitor can be further improved, and excellent ignitability can be maintained for a longer period of time.

Moreover, since BaTiO ₃ has a very high dielectric constant, the capacitance of the capacitor can be further increased. Therefore, the transmittance of AC power when AC power passes through the capacitor can be further improved, and the ignitability can be further improved.

Configuration 10 . In the ignition system of this configuration, in any one of the above configurations 1 to 9 , a portion of the discharge electrode and the AC electrode facing each other with at least the insulator interposed therebetween has a volume resistivity of 0.1 μΩ · m. It is characterized by being formed of a metal material having no magnetism below.

According to the configuration 10 , the loss of AC power during transmission can be further reduced, and the AC power input to the spark can be further increased. As a result, the ignitability can be further improved.

Configuration 11 . The ignition system of this configuration is the above configuration 10 , wherein the metal material is copper (Cu), silver (Ag), gold (Au), aluminum (Al), zinc (Zn), or any one of them. It is an alloy having a main component.

According to the above-described configuration 11 , the part of the electrode forming the capacitor that faces the insulator is formed of a metal material having a very small volume resistivity such as Cu or Ag. Therefore, the loss of AC power can be prevented more effectively, and the ignitability can be further improved.

It is a block diagram which shows schematic structure of an ignition system. It is a partially broken front view which shows structures, such as a spark plug. It is a schematic block diagram which shows structures, such as an ignition cable. It is a partial expanded sectional view which shows another example of an insulator. (A), (b) is the elements on larger scale which show another example of an insulator. It is a partially broken enlarged front view which shows the structure of the ignition cable etc. in 2nd Embodiment. It is a graph which shows the result of the ignitability evaluation test in the sample which changed the electrostatic capacitance of the capacitor. It is a graph which shows the result of the durability evaluation test in the sample which changed the constituent material of the insulator. It is a graph which shows the result of the ignitability evaluation test in the sample which changed the constituent material of the site | part which opposes on both sides of an insulator among discharge electrodes and an alternating current electrode. It is a graph which shows the relationship between the shortest distance between an alternating current electrode and a terminal metal fitting, and the discharge voltage at the time of the leak of an electric current producing between an alternating current electrode and a terminal metal fitting. It is a partially broken front view which shows the structure of the spark plug etc. in another embodiment. It is a partial expanded sectional view which shows the structure of the capacitor | condenser in another embodiment. It is a partial expanded sectional view which shows the structure of the capacitor | condenser in another embodiment. It is a partial expanded sectional view which shows the structure of the capacitor | condenser in another embodiment. It is a partial expanded sectional view which shows the structure of the capacitor | condenser in another embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of the ignition system 101. In FIG. 1, only one spark plug 1 is shown, but an actual engine EN is provided with a plurality of cylinders, and the spark plugs 1 are provided corresponding to the respective cylinders. And the electric power from the discharge power supply 2 and the alternating current power supply 3 which are described below is supplied to each spark plug 1 via the distributor which is not shown in figure.

  The ignition system 101 includes an ignition plug 1, a discharge power source 2, an AC power source 3, and an ignition cable 4.

  As shown in FIG. 2, the spark plug 1 includes a cylindrical insulator 12 having a shaft hole 14 extending in the direction of the axis CL <b> 1, a center electrode 15 and a terminal fitting 16 inserted through the shaft hole 14, and the insulator 12. A cylindrical metal shell 13 disposed on the outer periphery and a ground electrode 17 fixed to the tip of the metal shell 13 are provided. The center electrode 15 and the terminal fitting 16 are fixed to the insulator 12 by a conductive glass seal layer 18 and are electrically connected. The center electrode 15, the terminal fitting 16, and the glass seal layer 18 forms a plug electrode 11 through which a current from the discharge power source 2 or the AC power source 3 flows. A gap 19 is formed between the tip of the center electrode 15 and the tip of the ground electrode 17. The spark plug 1 is attached to a plug hole HO (attachment hole) formed in the engine EN. As a result, the metal shell 13 is in contact with the engine EN and is grounded.

  Returning to FIG. 1, the discharge power source 2 supplies a high voltage to the spark plug 1 and generates a spark discharge in the gap 19, and includes an ignition coil 21, a power supply battery 22, It has. The ignition coil 21 includes a primary coil 23, a secondary coil 24, a core 25, and an igniter 26.

  The primary coil 23 is wound around the core 25 and has one end connected to the battery 22 and the other end connected to the igniter 26. The secondary coil 24 is wound around the core 25, one end of which is connected between the primary coil 23 and the battery 22, and the other end is connected to the spark plug 1 via the ignition cable 4. Electrically connected.

  In addition, the igniter 26 is formed by a predetermined transistor, and switches between supply and stop of power supply from the battery 22 to the primary coil 23 in accordance with an energization signal input from an electronic control unit (ECU) 6 of the automobile. Is. When applying a high voltage to the spark plug 1, a current is passed from the battery 22 to the primary coil 23, a magnetic field is formed inside the core 25, and the energization signal from the ECU 6 is switched from on to off. Then, the current from the battery 22 to the primary coil 23 is stopped. When the current is stopped, the magnetic field of the core 25 changes, and a primary voltage is generated in the primary coil 23 by self-dielectric action, and the secondary coil 24 is negative and has a relatively low frequency high voltage (several to several 10 kV) is generated. When this negative high voltage is applied to the spark plug 1, spark discharge occurs in the gap 19 of the spark plug 1.

  The AC power source 3 supplies AC power to the spark plug 1 via an AC electrode 42 described later of the ignition cable 4. In the present embodiment, the oscillation frequency of AC power supplied from the AC power supply 3 is set to 50 kHz to 100 MHz (for example, 13 MHz to 42 MHz).

  In addition, the ignition cable 4 is for electrically connecting the spark plug 1 to the discharge power source 2 and the AC power source 3, and as shown in FIG. 3, the discharge electrode 41, the AC electrode 42, An insulator 43, a second insulator 44, and a shield member 45 are provided.

  The discharge electrode 41 electrically connects the secondary coil 24 of the discharge power supply 2 and the terminal fitting 16 of the spark plug 1, and the high voltage generated by the discharge power supply 2 (secondary coil 24) Is to be transmitted. In the present embodiment, the discharge electrode 41 is made of a metal material having a volume resistivity of 0.1 μΩ · m or less and having no magnetism. As the metal material, copper (Cu), silver (Ag), gold (Au), aluminum (Al), zinc (Zn), or an alloy mainly composed of any of these is used. .

  In addition, the spark plug side end 41A of the discharge electrode 41 is located closer to the spark plug 1 than the spark plug side end 42A of the AC electrode 42, and when the ignition cable 4 is connected to the spark plug 1, The spark plug side end portion 41 </ b> A is configured to contact the terminal fitting 16. Note that the spark plug side end 41A has a spring shape, and more stable contact between the discharge electrode 41 and the terminal fitting 16 is achieved.

  The AC electrode 42 is electrically connected to the AC power source 3 and serves as a transmission path for AC power when transmitting AC power from the AC power source 3 to the ignition plug 1 side. In the present embodiment, the AC electrode 42 is formed by forming a flat knitted lead wire (lead wire knitted into a flat plate shape) excellent in durability against bending and twisting into a cylindrical shape, and its inner peripheral surface is discharged. The discharge electrode 41 is disposed on the outer periphery so as to face the outer peripheral surface of the discharge electrode 41. Similarly to the discharge electrode 41, the AC electrode 42 is formed of a metal material having a volume resistivity of 0.1 μΩ · m or less and having no magnetism.

  The insulator 43 has a cylindrical shape and is disposed between the discharge electrode 41 and the AC electrode 42. The insulator 43 is made of an insulating ceramic. In this embodiment, barium titanate (BaTiO3) is used as the insulating ceramic. The insulator 43 may be formed using other ceramics (for example, PbTiO3, Al2O3, etc.), heat resistant resin, or the like. In addition, as shown in FIG. 4, without forming the insulator by a single ceramic, the ceramic 51 and a plurality of ring-shaped resins provided inside the ceramic 51 and arranged intermittently via the ceramic 51. The insulator 53 may be composed of (for example, an epoxy resin or the like) or rubber (for example, silicone rubber or fluorine rubber) 52. The insulator 53 has a pipe member formed by alternately laminating a ring-shaped ceramic ring member and a ring-shaped resin or rubber ring member. It can be obtained by providing a cylindrical member made of ceramic on the inner periphery and outer periphery of the pipe member. In the case where the insulator is formed of ceramic and resin or rubber, the shape of the insulator is not particularly limited. Therefore, for example, as shown in FIG. 5A, an insulator 56 in which ring-shaped ceramics 54 and resins or rubbers 55 are alternately laminated may be used, or FIG. As shown in FIG. 6, an insulator 59 in which a cylindrical resin or rubber 58 is disposed between the cylindrical ceramic 57 and the discharge electrode 41 and the AC electrode 42 may be used.

  Returning to FIG. 3, a cylindrical capacitor 46 is formed by the discharge electrode 41, the AC electrode 42, and the insulator 43 sandwiched between the electrodes 41 and 42. In the present embodiment, as described above, the oscillation frequency of the AC power supplied from the AC power supply 3 is set to 50 kHz or more and 100 MHz or less, and the capacitance of the capacitor 46 is set corresponding to this oscillation frequency. Yes. That is, when the capacitance of the capacitor 46 is C (F) and the oscillation frequency of the AC power is f (Hz), the capacitance of the capacitor 46 is set so as to satisfy C ≧ 0.0005 (F · Hz) / f. The capacity is set.

  The second insulator 44 is provided inside the shield member 45, and at least a part of the second insulator 44 is located on the outer peripheral side of the AC electrode 42. Further, the second insulator 44 includes a mounting hole 44H through which the insulator 12 and the terminal fitting 16 of the spark plug 1 are inserted when the ignition cable 4 is connected to the spark plug 1. Furthermore, the second insulator 44 is made of a predetermined insulating material (for example, resin or rubber) having a relatively small dielectric constant and plasticity. Therefore, the dielectric constant of the insulator 43 is larger than the dielectric constant of the second insulator 44.

  The shield member 45 is made of a cylindrical flat braided wire and is disposed on the outer periphery of the second insulator 44. Further, the end of the shield member 45 on the side of the spark plug 1 is in contact with the rear end of the metal shell 13 that is in contact with the engine EN and is grounded, so that the shield member 45 is grounded. (See FIG. 2). In addition, in the present embodiment, the shield member 45 and the cylindrical outer conductor 47 that is electrically connected to the shield member 45 and grounded are provided on the outer periphery of the conductive path of the AC power to the spark plug 1. Is provided. For this reason, in the conductive path of AC power, reflection of power and radiation of electromagnetic noise to the outside are prevented, and AC power is more reliably supplied to the spark plug 1.

  As described in detail above, according to the present embodiment, a spark is generated in the spark plug 1 by the voltage supplied from the discharge power source 2, and then the AC power from the AC power source 3 is applied to the spark. It is configured to be input. Accordingly, the spark is strengthened by the AC power, and the spark can be grown larger, and as a result, the ignitability can be dramatically improved.

  In addition, since a spark is generated by applying a voltage, it is difficult to cause a situation in which the required voltage cannot be output as in the case of generating a spark by supplying only AC power, and the occurrence of misfire can be more reliably prevented. it can.

  Furthermore, the ignition cable 4 includes a discharge electrode 41, an AC electrode 42, and an insulator 43 sandwiched between both electrodes 41, 42, and both electrodes 41 are interposed between the ignition plug 1 and the AC power supply 3. , 42 and a capacitor 46 formed of an insulator 43 is interposed. Accordingly, the AC power having a relatively high frequency with an oscillation frequency of 50 kHz or more is passed through the capacitor 46 and supplied to the spark plug 1, while the current having a relatively low frequency output from the discharge power source 2 is used. The presence of the capacitor 46 suppresses inflow to the AC power source 3 side. Therefore, a sufficient voltage can be applied to the spark plug 1 and a spark can be generated more reliably. Further, the presence of the ignition coil 21 can prevent the inflow of AC power to the discharge power supply 2 side. As a result, the above-described effect of improving the ignitability can be more reliably exhibited.

  In addition, according to the present embodiment, the oscillation frequency of AC power is set to a sufficiently small value of 100 MHz or less. Accordingly, the wavelength of the AC power can be made sufficiently large, the occurrence of resonance in the spark plug 1 and the ignition cable 4 can be prevented more reliably, and the above-described effect of improving the ignitability can be more reliably achieved. It can be demonstrated. In addition, since it is possible to prevent the occurrence of resonance without finely adjusting the design of the spark plug, etc., it is possible to secure a sufficient degree of freedom in the design of the spark plug and the like, and in addition, special adjustments have been made to the spark plugs that have been used in the past. It can be used as it is without applying.

  In addition, the capacitance C (F) of the capacitor 46 is set so as to satisfy C ≧ 0.0005 (F · Hz) / f with respect to the oscillation frequency f (Hz) of the AC power. Therefore, when the AC power passes through the capacitor 46, the loss of AC power is further reduced, and the ignitability can be further improved.

  In the present embodiment, the dielectric constant of the insulator 43 is larger than the dielectric constant of the second insulator 44. Therefore, it is possible to more reliably prevent the AC power input to the capacitor 46 (AC electrode 42) from being transmitted to the low potential side engine EN via the second insulator 44. As a result, the loss of AC power during transmission can be more reliably reduced, and sparks can be grown more effectively.

  In addition, since the insulator 43 is made of BaTiO3, which is extremely excellent in terms of heat resistance and voltage resistance, the durability of the capacitor 46 can be dramatically improved. As a result, excellent ignitability can be maintained over a longer period. Moreover, since BaTiO3 has a very high dielectric constant, the capacitance of the capacitor 46 can be further increased. Therefore, the transmittance of AC power when AC power passes through the capacitor 46 can be further improved, and the ignitability can be further improved. Furthermore, when the insulator is formed of a composite material of ceramic and resin or rubber, the resin and rubber function as a buffer material against mechanical shock and thermal shock, further enhancing the durability of the capacitor. It becomes possible to raise. Moreover, the flexibility of the ignition cable 4 is improved, and the handling of the ignition cable 4 is facilitated.

Further, the discharge electrode 41 and the AC electrode 42 are made of a metal material having a volume resistivity of 0.1 μΩ · m or less and having no magnetism. For this reason, the loss of the alternating current power at the time of transmission can be reduced further, and the alternating current power thrown into the spark can be further increased. As a result, the ignitability can be further improved.
[Second Embodiment]
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, the ignition cable 4 includes the insulator 43. However, in the second embodiment, as shown in FIG. 6, the insulator 12 included in the spark plug 1 is the first insulator. It is comprised so that the function equivalent to the insulator 43 in embodiment may be exhibited.

  That is, the ignition cable 7 according to the second embodiment includes a discharge electrode 71 whose end on the ignition plug side is connected to the terminal fitting 16 (plug electrode 11), and the ignition plug side in a state where the ignition cable 7 is connected to the ignition plug 1. An AC electrode 72 is provided on the outer periphery of the insulator 12 so that the end portion sandwiches the insulator 12 between the terminal fitting 16 (plug electrode 11). In the state where the ignition cable 7 is connected to the ignition plug 1, the plug electrode 11 (terminal fitting 16), the AC electrode 72, and the insulator 12 are sandwiched between the plug electrode 11 (terminal fitting 16) and the AC electrode 72. The capacitor 73 is formed by the different parts. When the capacitance of the capacitor 73 is C (F) and the oscillation frequency of the AC power is f (Hz), the AC with respect to the plug electrode 11 satisfies C ≧ 0.0005 (F · Hz) / f. The facing area of the electrode 72, the thickness of the insulator 12, and the like are set.

  In the second embodiment, the shortest distance SL1 along the surface of the insulator 12 between the AC electrode 72 and the metal shell 13 and between the AC electrode 72 and the plug electrode 11 (terminal metal fitting 16). The relative position of the AC electrode 72 with respect to the spark plug 1 when the ignition cable 7 is attached to the spark plug 1 is set so that the shortest distance SL2 along the surface of the insulator 12 is 5 mm or more.

  Further, an annular connector spring 72C as a tightening portion is provided at the end of the AC electrode 72 on the spark plug side. Thereby, in a state where the ignition cable 7 is connected to the ignition plug 1, the AC electrode 72 can tighten the insulator 12 in the radial direction. An annular connector spring 74C is also provided at the end of the shield member 74 of the ignition cable 7 on the side of the spark plug. When the ignition cable 7 is connected to the spark plug 1, the shield member 74 attaches the metal shell 13 to the end. It can be tightened in the radial direction.

  The insulator 12 is made of an insulating ceramic (for example, BaTiO3, PbTiO3, Al2O3, etc.). Further, the portions of the discharge electrode 71 and the AC electrode 72 that face each other across the insulator 12 have a volume resistivity of 0.1 μΩ · m or less and no magnetism, as in the first embodiment. It is comprised with the metal material (For example, Cu, Ag, Au, Al, Zn, or the alloy which has either of these as a main component).

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment are basically obtained.

  In addition, since the capacitor 73 is formed using the insulator 12 that the spark plug 1 generally has, the manufacturing cost can be effectively reduced as compared with the case where the capacitor is provided in the ignition cable.

  Furthermore, since the connector spring 72A is provided at the end of the AC electrode 72 on the spark plug 1 side, the insulator 12 and the AC electrode 72 can be more stably connected. As a result, the capacitor 73 can be more reliably formed by the plug electrode 11, the insulator 12, and the AC electrode 72.

  Further, the shortest distance SL1 along the surface of the insulator 12 between the AC electrode 72 and the metallic shell 13 and the surface of the insulator 12 between the AC electrode 72 and the plug electrode 11 (terminal fitting 16). In addition, the shortest distances SL2 are secured sufficiently large at 5 mm or more. Accordingly, current leakage between the AC electrode 72 and the metallic shell 13 or the terminal fitting 16 can be prevented more reliably, and as a result, the occurrence of misfire can be more effectively suppressed.

  Next, in order to confirm the operational effects exhibited by the above-described embodiment, samples of the ignition system in which the capacitance of the capacitor was variously changed were produced, and an ignitability evaluation test was performed on each sample. The outline of the ignitability evaluation test is as follows. That is, the spark plug of each sample was attached to a 2000 cc displacement 4-cylinder DOHC engine, and the air-fuel ratio (A / F) was set to 17. Then, after setting the power of the AC power supply to 300 W, the power frequency of the AC power was changed to 100 MHz, 10 MHz, 1 MHz, or 50 kHz, and power was applied 1000 times to each sample. While measuring the number of misfires (abnormal discharge), the occurrence rate of misfires (misfire rate) was calculated. FIG. 7 shows the test results of the test. In FIG. 7, the test results when the transmission frequency is 100 MHz are indicated by circles, and the test results when the transmission frequency is 10 MHz are indicated by triangles. Moreover, the test result when the transmission frequency is 1 MHz is indicated by a square, and the test result when the transmission frequency is 50 kHz is indicated by a cross mark.

  As shown in FIG. 7, when the transmission frequency is 100 MHz, the capacitance of the capacitor is 5 pF or more. When the transmission frequency is 10 MHz, the capacitance of the capacitor is 50 pF or more. Thus, when the transmission frequency is 1 MHz, the capacitance of the capacitor is 500 pF or more, and when the transmission frequency is 50 kHz, the capacitance is 10000 pF or more, that is, the transmission frequency is f (Hz) and the capacitance of the capacitor is C (F). By setting the capacitance of the capacitor so as to satisfy C ≧ 0.0005 (F · Hz) / f, the misfire rate Was less than 3%, and it became clear that excellent ignitability could be realized. This is considered to be because the AC power is more reliably transmitted through the capacitor by increasing the capacitance of the capacitor, and the AC power is more reliably supplied to the spark.

  From the above test results, it can be said that it is preferable to set the capacitance of the capacitor so as to satisfy C ≧ 0.0005 (F · Hz) / f in order to improve the ignitability.

Next, a sample of an ignition system in which an insulator is made of polyphenylene sulfide resin (PPS), lead titanate (PbTiO ₃ ), barium titanate (BaTiO ₃ ), or a composite material of BaTiO ₃ and silicone rubber (Si rubber). And a durability evaluation test was performed on each sample. The outline of the durability evaluation test is as follows. That is, after attaching a sample spark plug to a 4-cylinder DOHC engine with a displacement of 2000 cc, the engine was operated for 30 minutes in a fully open state (= 4000 rpm), and then idling for 30 minutes. Among these, the time (durability time) until penetration occurred in a portion sandwiched between the discharge electrode and the AC electrode (that is, a portion forming a capacitor) was measured. FIG. 8 shows the test results of the test. In each sample, the capacitance of the capacitor was 200 pF. The output power of the AC power supply was 300 W, and the oscillation frequency of the AC power was 50 MHz.

As shown in FIG. 8, a sample in which the insulator is formed of ceramic (PbTiO ₃ or BaTiO ₃ ) or a composite material having excellent heat resistance has excellent durability, and in particular, the insulator is formed of BaTiO ₃ . The sample had a durability of about 400 hours and was confirmed to have a very excellent durability.

  Moreover, it was confirmed that the sample in which the insulator is formed of a composite material of ceramic and rubber has an extremely excellent durability, with a durability time exceeding 1000 hours. This is presumably because rubber functions as a buffer against thermal expansion such as vibration and electrodes, and the strength of the capacitor against mechanical shock and thermal shock is improved. In the above test, a test was performed using a composite material made of ceramic and rubber. However, it is considered that the same result can be obtained even when a resin is used instead of rubber.

From the above test results, it can be said that it is preferable to form the insulator with ceramic, and it is more preferable to form the insulator with a composite material such as BaTiO ₃ , ceramic and rubber in order to improve durability.

  Next, samples of the ignition system in which various constituent metals of the discharge electrode and the AC electrode facing each other with the insulator interposed therebetween were produced, and the above-described ignitability evaluation test was performed on each sample. FIG. 9 shows the test results of the test. Table 1 shows the volume resistivity and the presence or absence of magnetism in each metal. The capacitance of the capacitor and the transmission frequency of the AC power were set so as to satisfy C ≧ 0.0005 (F · Hz) / f.

  As shown in FIG. 9 and Table 1, each sample had a misfire rate of less than 3.0% and had excellent ignitability, but in particular, the volume resistivity was 0.10 μΩ · m or less, and The sample using a metal having no magnetism had a misfire rate of less than 1.0%, and was found to be extremely excellent in ignitability. This is presumably because the loss of AC power during transmission was suppressed and the AC power input to the spark was further increased.

  In particular, it has been confirmed that a sample using Cu, Ag, Au, Al, or Zn as the metal material can realize better ignitability.

  From the above test results, in order to further improve the ignitability, the volume resistivity is 0.1 μΩ · m or less at a portion facing each other with at least the insulator between the discharge electrode and the AC electrode, and It can be said that it is preferable to form a metal material having no magnetism. Among such metal materials, Cu or Ag having a relatively low volume resistivity, or a metal having any one of them as a main component is used in terms of realizing even better ignitability. It is even more preferable.

  Next, in the ignition system corresponding to the second embodiment, a sample of the ignition system in which the shortest distance along the outer surface of the insulator between the AC electrode and the terminal metal fitting is variously changed is prepared, and discharge is performed in each sample. The voltage applied to the electrode for use (the voltage of the power supply for discharge) was gradually increased, and the discharge voltage when current leakage occurred between the AC electrode and the terminal fitting was measured. FIG. 10 shows the test results of the test.

  As shown in FIG. 10, it was found that the sample having the shortest distance of 5 mm or more had a discharge voltage of 30 kV or more, and current leakage was extremely difficult to occur.

  From the above test results, it can be said that the shortest distance is preferably 5 mm or more in order to prevent current leakage. In addition, it can be said that the shortest distance along the outer surface of the insulator between the AC electrode and the metal shell is preferably 5 mm or more in order to prevent current leakage between the two.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the second embodiment, the plug electrode 11 includes the center electrode 15, the terminal fitting 16, and the glass seal layer 18. As shown in FIG. The resistor 82 (for example, a fired resistor composition including a conductive material and glass powder) may be interposed in the plug electrode 81. When the resistor 82 is provided, the resistor 82 is formed by the AC electrode 72, the plug electrode 81, and the portion of the insulator 83 that is sandwiched between the ignition cable 7 and the spark plug 8 when the ignition cable 7 is connected to the spark plug 8. The capacitor 84 is preferably provided on the tip side of the spark plug 1 relative to the resistor 82 (that is, on the side of the gap 87 formed between the center electrode 85 and the ground electrode 86). In this case, since the resistor 82 exists only on the conductive path of the voltage from the discharge power supply 2 and does not exist on the conductive path of the AC power, loss of AC power by the resistor 82 is prevented. Thus, the effect of improving the ignitability can be more reliably exhibited.

  (B) In the first embodiment, the capacitor 46 has a configuration in which the cylindrical AC electrode 42 is provided on the outer periphery of the discharge electrode 41, but the configuration of the capacitor is not particularly limited. Therefore, for example, as shown in FIG. 12, the discharge electrode 91 is disposed on the outer peripheral side, and the AC electrode 92 is disposed on the inner peripheral side (that is, the capacitor is configured by exchanging positions of both electrodes). 93 may be used. In this case, the spark plug side end portion 91A of the discharge electrode 91 is located closer to the spark plug 1 side than the spark plug side end portion 92A of the AC electrode 92, and the spark plug side end portion of the discharge electrode 91 is located. 91A is connected to the spark plug 1.

  As shown in FIG. 13, a capacitor 97 in which a plate-like discharge electrode 94 is opposed to the plate-like AC electrode 96 with an insulator 95 interposed therebetween may be used. Furthermore, as shown in FIG. 14, in the cross section orthogonal to the longitudinal direction of the ignition cable, at least a part of the discharge electrode 111 having a spiral shape and at least a portion facing the spiral portion of the discharge electrode 111 is spiral. Alternatively, a capacitor 114 including the AC electrode 112 and the spiral portion of the discharge electrode 111 and the insulator 113 disposed between the spiral portion of the AC electrode 112 may be used. In addition, by configuring the spiral portion of the discharge electrode 111 and the AC electrode 112 so as to extend along the longitudinal direction of the ignition cable, a large facing area between both the electrodes 111 and 112 can be secured, and the capacitor 114 Can be easily increased.

  In addition, as shown in FIG. 15, the first main electrode plate 115A and a plurality of first auxiliary electrodes extending from the first main electrode plate 115A and arranged along the direction orthogonal to the longitudinal direction of the first main electrode plate 115A. A discharge electrode 115 having an electrode plate 115B, a second main electrode plate 116A extending along the longitudinal direction of the discharge electrode 115 and facing the first main electrode plate 115A, and a second main electrode plate 116A; AC electrode 116 having a plurality of second auxiliary electrode plates 116B arranged alternately with first auxiliary electrode plates 115B along a direction orthogonal to the longitudinal direction of second main electrode plate 116A (ie, each has a comb-tooth shape in cross section). A capacitor 118 having electrodes 115 and 116) and an insulator 117 disposed between both auxiliary electrode plates 115B and 116B may be used.

  Note that the capacitors 97, 114, and 118 may be arranged on the inner periphery of the cylindrical second insulator. In this case, it is preferable that the dielectric constant of the insulator is larger than the dielectric constant of the second insulator.

  (C) In the above embodiment, the electric power from the discharge power source 2 and the AC power source 3 is supplied to each spark plug 1 via the distributor, but the discharge power source 2 and the AC power source 3 are provided for each spark plug 1. It is good also as providing.

DESCRIPTION OF SYMBOLS 1 ... Spark plug 2 ... Power supply for discharge 3 ... AC power supply 4 ... Ignition cable 11, 81 ... Plug electrode 41 ... Electrode for discharge 42 ... AC electrode 43 ... Insulator 44 ... 2nd insulator 72C ... Connector spring (clamping part) )
82 ... resistor 115A ... first main electrode plate 115B ... first auxiliary electrode plate 116A ... second main electrode plate 116B ... second auxiliary electrode plate CL1 ... axis

Claims (11)

Spark plugs,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
The cylindrical AC electrode is disposed on the inner periphery of the second insulator,
The cylindrical insulator is disposed on the inner periphery of the AC electrode,
The discharge electrode is disposed on the inner periphery of the insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug . Spark plugs,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
The discharge electrode, at least a part of which is cylindrical, is disposed on the inner periphery of the second insulator,
The cylindrical insulator is disposed on the inner periphery of the cylindrical portion of the discharge electrode,
The AC electrode is disposed on the inner periphery of the insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug . Spark plugs,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
At least a part of the discharge electrode has a plate shape,
Of the AC electrode, at least a portion facing the plate-like portion of the discharge electrode has a plate shape,
The insulator is disposed between the plate-like portion of the discharge electrode and the plate-like portion of the AC electrode,
The electrodes and the insulator are disposed on the inner periphery of the second insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug . Spark plugs,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
In a cross section perpendicular to the longitudinal direction, at least a part of the discharge electrode has a spiral shape,
Of the alternating current electrode, at least a portion facing the spiral portion of the discharge electrode has a spiral shape,
The insulator is disposed between the spiral portion of the discharge electrode and the spiral portion of the AC electrode,
The discharge electrode, the AC electrode, and the insulator are disposed on an inner periphery of the second insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug . Spark plugs,
A discharge power source for applying a voltage for generating a spark discharge in the spark plug;
An AC power supply for supplying AC power to the spark generated by the spark discharge;
An ignition system comprising: an ignition cable that electrically connects the spark plug to the discharge power source and the AC power source,
The ignition cable is
A discharge electrode for connecting the discharge power source and the spark plug to apply a voltage from the discharge power source to the spark plug;
An AC electrode for transmitting AC power from the AC power source to the spark plug side;
An insulator sandwiched between the electrodes;
A cylindrical second insulator,
The second insulator is at least partially disposed on the outer peripheral side of the discharge electrode, the AC electrode, and the insulator,
The dielectric constant of the insulator, much larger than the dielectric constant of the second insulator,
The ignition cable is
The discharge electrode includes a first main electrode plate extending along a longitudinal direction, and a plurality of first auxiliary electrode plates extending from the first main electrode plate and arranged along a direction orthogonal to the longitudinal direction,
The AC electrode includes a second main electrode plate extending along the longitudinal direction, and a plurality of second auxiliary electrode plates extending from the second main electrode plate and arranged along a direction orthogonal to the longitudinal direction,
The discharge electrode and the AC electrode are arranged so that the first main electrode plate and the second main electrode plate face each other and the first auxiliary electrode plate and the second auxiliary electrode plate are alternately arranged. And
The insulator is disposed between the auxiliary electrode plates;
The discharge electrode, the AC electrode, and the insulator are disposed on an inner periphery of the second insulator,
An ignition system, characterized in that the spark plug side end of the discharge electrode is connected to the spark plug . The oscillation frequency of the AC power is 50 kHz or more and 100 MHz or less,
The capacitance of the capacitor formed by the discharge electrode, the alternating current electrode, and the insulator is C (F),
When the oscillation frequency of the AC power is f (Hz),
C ≧ 0.0005 (F · Hz) / f
The ignition system according to any one of claims 1 to 5, wherein: The ignition system according to any one of claims 1 to 6, wherein the insulator is made of a composite material of ceramic and resin or rubber. The insulator, the ignition system according to any one of claims 1 to 6, characterized in that it is formed by ceramic. The ignition system according to claim 7 or 8 , wherein the ceramic is mainly composed of barium titanate. Of the discharge electrode and the AC electrode, at least a portion facing the insulator is formed by a metal material having a volume resistivity of 0.1 μΩ · m or less and having no magnetism. The ignition system according to any one of claims 1 to 9 , characterized in that: 11. The ignition system according to claim 10 , wherein the metal material is copper, silver, gold, aluminum, zinc, or an alloy containing any one of them as a main component.

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